Sal Suds or Castile Soap – Which One Should You Use?

I talk a lot about the exceeding versatility of Dr. Bronner’s Castile Soap and Dr. Bronner’s Sal Suds.  There are so many overlapping uses.  But is there any time in which they aren’t interchangeable?  Yes, but just a few.

Castile soap is primarily designed for the body.  The blend of oils (coconut, olive, palm, jojoba, and hemp) are designed to be the most nourishing to our skin.  But wait, there’s more.  Because it is such a beautifully simple soap, it also cleans many other things amazingly well, whether it’s your dog, your sinks, or your floors. You can find details of all these uses on this Castile Soap Dilutions Cheat Sheet.

Because Castile soap is a true soap, it reacts with the minerals contained in hard water. (Here’s my test to find out if you have hard water.)  The more dissolved minerals there are, the “harder” the water.  The reaction of soap with these minerals in the water leaves behind an insoluble film that’s commonly called “soap scum”.  This term is a bit of a misnomer, because it’s not actually soap that remains, but a precipitate of minerals.

You’ll only notice this on shiny objects that are left to air dry.  They will take on a whitish film. (Read my post on eliminating soap scum.) Also, absorbent fabrics like towels and cloth diapers will become stiff and lose their absorbency. (But laundry in hard water is still doable – Read more here.)

Enter Sal Suds.  This is our biodegradable household cleaner developed by my dad. Sal Suds doesn’t react with hard water.  It rinses cleanly and leave surfaces sparkling.  No more film on the tub or towels!  For it’s multitude of uses, see the Sal Suds Dilution Cheat Sheet.

That’s all well and good, but I haven’t answered that initial question of what to use when.

Situations where I exclusively use Castile:

  • Myself – Head to toe.
  • My animals – Any Castile soap scent on my dog. Baby Unscented on my cat.
  • Pest Control – Only Castile soap has this ability to eliminate insects.

Situations where I exclusively use Sal Suds:

  • Dishes
  • Cars
  • Most Laundry – sometimes, as with bedding, I use Castile soap.

Other than these few cases, I reach for whichever is closer at hand.

Now you know what to use, but perhaps you want to know why?

Soap and detergent are both surfactants.  The word “surfactant” is a portmanteau of “Surface Active Agent.”  If you’ve ever done a belly flop into a pool, then you’ve felt the power of surface tension. Surfactants break through the surface tension of water and make water really soak in.

My brother Mike says that:

Surfactants make water wetter.

The second magical power of surfactants is that they make oil and water coexist.  Which they don’t otherwise like to do.  This is why you can’t just rinse oil off your hands.  The water runs over the oil like it’s just not there.  And it just doesn’t care.

Now brace yourselves – you’re about to learn some Greek!

Surfactants solve the oil/water repulsion because one end of each surfactant molecule is hydrophilic and the other end is hydrophobic.

Hydrophilic literally means “water (hydro) loving (philic).”  This end of the surfactant molecule grabs hold of water.  On the other side, hydrophobic means “water (hydro) fearing (phobic).”  A little exaggerated perhaps, but this end grabs the oil.

But we’re not talking about just one.  Surfactant molecules work in groups.  In a solution, they float around looking for oil molecules and snag with those hydrophobic tails, totally surrounding each oil molecule so there’s no part of the oil molecule left exposed to water.  This little nugget is called a micelle.

The outside of this micelle is now entirely hydrophilic, which means instant attraction to the passing rinse water which carries it all away.

It’s like they’re filling those oil molecules with a whole lotta love and reaching out and connecting them with their former enemy, those water molecules.  And once they’re connected, they realize it’s not so bad.  They can get along. They can hang out together.  I think there’s a larger lesson here.

You still with me?

So they’re both surfactants.  Now for some differences.

Soap is close to nature, made by a beautifully efficient one-step reaction of combining oil (coconut, palm, olive, jojoba, and hemp for our Castile) with a strong alkali such as sodium or potassium hydroxide (the first also known as lye).  Out of this combo, you get soap, glycerin and water. Bam!  No leftovers. No waste. Beautiful.

Detergents are more complex and must be synthesized.  They were developed during the World Wars when the oils needed for soap were scarce.  They can start with botanical substances (such as coconut oil for our Sal Suds) or with petroleum derivatives. And the uses of detergents is vast and wide.

Tidy as it would be, I can’t sum it all up by saying, “Soap good. Detergent bad.”  That would be a gross oversimplification.  There are bad soaps (not ours, of course) that are poorly made with bits of unreacted alkali floating around in them ready to saponify your very body.  You become walking bar of soap.  Ouch!

And there are excellent detergents, such as our Sal Suds, which is super duper tough on grease and completely clean rinsing, yet mild and biodegradable.

So that’s a little bit more about the magic of cleaning and the beauty of chemistry.

143 thoughts on “Sal Suds or Castile Soap – Which One Should You Use?

  1. Hello!
    I’m living in New Zealand and not able to find Sal Suds (without exuberant shipping costs). I’d like to use it for laundry but since I can’t get it, am I able to substitute with something else? I am able to get castille soaps.

  2. Hello
    So we love Dr Bronner’s and want to switch to using this product for our laundry.
    I have sensitive skin and when I use your Castle Soap on my laundry it comes out so nice and soft.
    Do you think the Sal Suds will give the same effect?

    • Hi Diane- Sal Suds is my go-to for laundry. It rinses exceedingly clean, leaving fabrics soft and free of residue.

  3. I bought the Castile soap to put in my homemade laundry detergent, and then I read your post on the Sals Suds. So, I am wondering would it be beneficial to put both in my laundry detergent?

  4. I love cleaning with your peppermint castile liquid soap. I just purchased my first bottle of Sals Suds. After mopping my floors with Sals, do I have to rinse/mop as well? I have dogs in my home and don’t want them picking up anything on their paws that can be harmful. Thank you! –Also, I just tried the rose bar soap for the first time. LOVED IT!!!!!!!!!!! It was so creamy and left my skin feeling so soft. Thank you!

  5. For some cleaning purposes, I like to use two different cleaning agents. Is it possible to use castile soap and Sal Suds simultaneously. I know that castile soap and vinegar cannot be used at the same time because they cancel each other out. Does the same happen when using castile soap and Sal Suds together at the same time (e.g., in laundry)? Thanks!

    • Hi Ash- Both are exceedlingly effective cleaners all on their own. There’s no need to mix them. But chemically speaking, there are no adverse effects if you were to do so.

  6. Hi there Lisa,

    I love your posts and the amount of detail you include. Very helpful, thank you!
    Do you own cats? I’m conscious that cats are sensitive to a lot of smells and essential oils. While I do not use any bronner’s products ON my cat (yes I know the unscented Castile soap is ok), I’m also wondering how sensitive cats are exactly and whether it’d be ok to use bronner’s soaps (Castile and sal suds) on items that the cat will use? Looking forward to your reply.

    • Hi Stephanie- It’s great to hear you find my posts helpful! The behavior of my two cats – who very much enjoy sleeping on freshly washed bedding, gobbling from their food dishes, and lounging on the clean tile flooring without a care in the world – leads me to believe they are not sensitive to the scent of our soaps. Cute cat habits aside though, the soap is most often diluted upon use and then rinsed off, leaving little to no scent behind.

  7. I live the eco-friendly lifestyle and like green cleaning. Thank you that you use recycled bottles for your castile soap! It’s very important for me because I avoid using plastic. I have a question can I wash my hair with your soap?

    • Hi Joshua – Well done! If everyone does their part, we all add up to massive change. Yes, the soap can wash hair, too! I made the switch a very long time ago, and my long hair is in great shape. I wrote about it in my post From Shampoo to Soap. One key to remember is that it takes hair a bit to acclimate. YOu might want to alternate with your current shampoo for a couple weeks before you switch completely.

  8. Hi Sal Suds sounds great but comes in a plastic bottle and I’m trying to cut back on plastic… would Castile soap in a bar work for dishes do you think even if not as well?

    • Hi Fiona – The bar soap works pretty well on dishes, though perhaps not quite as well as the Sal Suds. I recommend keeping a bar by the sink and using a dish brush. Wet the brush. Run it across the bar of soap, and you’ll have a good amount of soap for getting those dishes clean.

  9. Lisa,

    When grilling out, I wash my grill’s grates in my backyard, over my grass. In the past, when I used a store-bought detergent for dishes, it would kill my grass where it was rinsed off the grates. Since Sal Suds is a detergent, will it also kill my grass? Or, since it’s so mild, will I be okay? It sounds as though it will cut through the grease on the grates better than your Castile soap, so that’s why I’m asking. Thanks!

    • Hi Wayne- Sal Suds is tougher on grease, although both Sal Suds and Castile are biodegradable and won’t harm plants or grass.

  10. I was considering trying your Castile soap as my skin is dry, but then I noticed it has palm oil. Growers who plant palm orchards are destroying huge swaths of jungle which is endangering orangutans & many other species that live in the jungles. I will not purchase any products that contain palm oil. I’m sure you can find a way to eliminate it, so let me know when that happens. I’ll try it then. Thanks for listening.

    • Hi Elizabeth- This is such an important issue. I’m glad you brought it up. This is a concern that we share. The vast majority of palm oil used in food and body care products is sourced from southeast Asia with devastating results. I am happy to say that there are ways to produce palm oil that do not have this impact. In searching for options, our company partnered with small scale farmers in Ghana and founded Serendipalm, a sister company, that is producing palm oil in a way that promotes health not only to the environment and farmers, but also to the communities around it. Please read more about it here: https://www.drbronner.com/about/our-suppliers/projects-and-partnerships/#about-palm-oil. And here’s a video of our work in Ghana: Sustainable Palm Oil: The Difference Fair Trade Makes (https://www.youtube.com/watch?v=z2q0O4SlY9g#about-palm-oil).

  11. Hi there, I’m on a mission to go green with my household cleaners and have been working up to buying Sal Suds. But I suddenly realised I hadn’t read anywhere that you can use it in a dishwasher, and on googling found some recipes using your Castile soap. However in this post you highlight Sal Suds for dishes…can you use it in the dishwasher? Also we are about to make new kitchen worktop out of old scaffolding boards – can you use either one on (an oiled) wooden surface? Thanks!

    • Hi Anna- It’s great to hear you’re on a green mission! Sal Suds is my go-to for handwashing dishes, but unfortunately, it is too bubbly for the dishwasher. You can search for one in the EWG’s Guide to Healthy Cleaning (https://www.ewg.org/guides/cleaners). Your new kitchen worktop sounds beautiful! From what I’ve read, the recommended cleaning for re-purposed scaffolding is soap and water, in which case Sal Suds and water would work great. I do recommend spot testing it first though. Let me know how it works for you.

  12. it is advised to use a liquid soap when mixing Neem oil concentrate with water. Should I use Sal Suds or Castile Soap for this?

    • Hi Arun- It depends on what you will be using the soap and Neem oil for. If it is for use on the skin or body, use the Castile soap. Sal Suds is our all-purpose household cleaner.

  13. Can Sal Suds be used in hand soap? I know you explained in previous comments that head to toe you use Castile Soap but when washing dishes by hand with the Sal Suds in an essential oil dish detergent recipe it is touching our hands of course.

    • Hi Christina- It is safe, but more drying to hands than our Castile soap. Although no more so than a conventional soap.

  14. I live on Vancouver Island in Canada and would like to purchase Dr. Bonner’s Sal Suds. Can you tell me where I can buy it? I’m in Sidney/Victoria area.

    • Hi Susan- Our products are usually found in the body care section of most natural grocers, supermarkets and pharmacies. A distributor in your area also can tell you what stores in your area carry our products. Here’s a list of distributors: https://www.drbronner.com/wholesale/international/

  15. I was surprised to see sodium lauryl sulfate in the ingredient list for Sal Suds. I’ve seen it on the list of questionable ingredients for personal care products. It makes me very hesitant to buy Sal Suds. Can you explain why it is an ingredient in an all natural product?

    • Hi Lori- It’s great to hear you’re a fellow label reader! First, Sal Suds not a true soap like our Castile soaps. It is a biodegradable, all-purpose household detergent – meaning it is synthetic. But not everything synthetic is bad, in the way that not everything natural is good. Sal Suds is formulated with SLS because of its keen ability to cut through grease and grime and to generate suds. SLS can be a skin irritant for some people because it can be so drying. It is so good at picking up oils that it pulls them right out of our skin. You won’t find SLS in any of our personal care products, and personal care products (shampoos, soaps, toothpaste and such) that include it should be avoided. Studies have consistently shown that SLS is safe to use in low concentrations and in products that are meant to be rinsed off – both of which are true of Sal Suds. Of course our all-natural Castile soap does an excellent job of household cleaning as well. For a deeper dive into SLS, refer to my blog post here: http://www.lisabronner.com/there-is-no-cancer-risk-from-sls-sodium-lauryl-sulfate/.

    • Thank you for your response! I did read on some of the older questions/answers and you addressed the SLS questions very well! I have absolutely no hesitation now to purchase Sal Suds! I’m glad your company is so concientious about product quality and being earth friendly!

  16. We will be putting in Dekton countertops in our home and I was wondering if the Castile or Sal Suds work on this surface.

    • Hi Lisa- Either Sal Suds or Castile soap will clean your beautiful new countertops… well, beautifully!

  17. Does Sal Suds have a germ-killing, antibacterial properties in it? In other words, do the EO’s have those properties? Thanks.

    • Hi Andrea- The term “antibacterial” means that the product must kill 99.9% of germs. The term “disinfectant” means that the product must kill 99% of germs. Dr. Bronner’s soap (Castile soap and Sal Suds) is part of the “disinfectant” category. Soap works by removing. It latches on to dirt, grime, germs, etc. and takes them away. It’s the soap that’s doing the heavy lifting here, not the essential oils. The only thing that kills bacteria is a pesticide, and soap is not a pesticide. That means the short answer is, no, soap will not kill bacteria or anything else. Soap eliminates it, though. This is a question I get a lot – and it’s a good one – so I wrote about it in-depth recently: http://www.lisabronner.com/ditch-the-antibacterial-soap-is-all-you-need/.

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